[mythtv-users] Sandy Bridge Graphics w/MythTV

[jzigpublic]

On 7/22/2011 11:54 AM, Michael T. Dean wrote:
> On 07/22/2011 11:58 AM, jzigpublic wrote:
>> I came across the following solution for Sandy Bridge Video Tearing in
>> MythTV.  The quote was pulled from this site:
>> https://bugs.freedesktop.org/show_bug.cgi?id=37686
>> It worked for me with an i3 CPU and an Intel motherboard with Intel
>> HD2000 on-board graphics.  No more tearing.  I'm using MythBuntu 11.04.
>>
>>> In order to play 1080i video content on my system running mythbuntu-11.04, I
>>> created a new playback profile modeled after the "High Quality" playback
>>> profile.  The new profile differs in that it uses xshm for the video renderer
>>> (as opposed to xv-blit).  Please note that xshm says that it cannot scale video
>>> in case this a problem for your setup
>
> FWIW, Xshm is a terrible renderer to use for video.  It's extremely
> inefficient and, as mentioned, has issues such as lack of scaling, etc.
>
> Xv, which is likely what you were using when you noticed the tearing,
> should automatically prevent tearing, though some video drivers do
> require flipping a switch--probably labeled something like, "Work
> properly," or "Do the right thing," or, "Sync to vblank" (OK, really,
> not like the first two, but...) in some configuration program.  But, it
> is possible that the drivers for the new Sandy Bridge graphics are
> broken and don't properly handle sync for Xvideo.
>
> See http://www.gossamer-threads.com/lists/mythtv/commits/451677#451677
>
> That said, Xv is a 20+ year old API that shouldn't be the focus of
> modern hardware/drivers.  Instead, you may want to try the OpenGL
> renderer (which is a much more modern approach to video--rather than
> Xshm, which is a step back even from Xv).  Again, you may need to set
> some driver-specific video-syncing switch to prevent tearing (and your
> drivers may have a different switch for Xv and OpenGL video).
>
> With the OpenGL renderer, you'll also get additional benefits, such as a
> full-resolution (rather than video-resolution) OSD (meaning the OSD
> won't be squished to fit in a 4:3 video you're playing back with
> letterboxing on your widescreen display, and OSD fonts will look pretty
> even on standard definition video played back on your high-definition
> display).  The Sandy Bridge graphics should have sufficiently-powerful
> OpenGL capabilities to allow use of the OpenGL video renderer.
>
> Mike
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Unfortunately, My Sandy Bridge and  OpenGL stutters on MythTV 
recordings, so I guess there isn't enough horsepower there.  And 
you're right Xshm has it's problems too.


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